(1) Field of the Invention
The present invention relates to mixing-grade, quick-setting cationic aqueous bituminous emulsion-aggregate paving slurry seal mixtures. More particularly, this invention relates to slurries formed with cationic emulsions prepared by emulsifying bitumen, such as an asphalt, in water with a cation-active emulsifier which is the product of the reaction of modified polyamine with certain polycarboxylic acids. Most particularly, this invention relates to the employment of these cation-active emulsifiers which have been post-reacted with from 10-30% of a member of the group consisting of acetic anhydride, phthalic anhydride, propylene carbonate, and styrene oxide.
(2) Description of the Prior Art
Conventionally, emulsion slurry seals are formulated from (1) mineral aggregate which is a fine stone aggregate and/or mineral filler and (2) about 15% to about 25% by weight thereof of a mixing-grade, quick-setting or slow-setting emulsion containing from about 50% to about 75% by weight of bituminous residue (usually asphalt), with a further addition of about 5% to about 25% of water, based on the weight of the dry aggregate, to attain slurry consistency. Usually, densely-graded aggregates, such as granite screenings, limestone screenings, dolomite screenings and blast furnace slag, are combined with bituminous emulsions to produce slurry seal compositions. These aggregates range in size from anything passing all through a sieve of No. 4, and even No. 10 mesh, with from 15% to 20% passing through as fine a mesh as 200 mesh, as described in ASTM C136.
The advent of slurry seal as a paving and road maintenance technique was first developed for use with anionic aqueous bituminous emulsions. A slurry seal is an intimate mixture of emulsified bituminous material and fine-grained aggregate held in suitable suspension until applied to the road surface. The slurry seal emulsion must be of an oil-in-water type. In such a mixture with aggregate, the aqueous emulsion form of the bituminous material has been generally preferred because it is less hazardous and more economical to use than hot mix or cutback (solvent containing) asphalts. Further, the aqueous emulsion form can be stored, transported and applied at much lower temperatures, obviating the necessity of heating equipment to maintain a bitumen-aggregate system in a workable or usable form. While these advances have been recognized, widespread acceptance has not been achieved due to disadvantages found in previous aqueous bituminous emulsions.
More recently, cationic bituminous emulsions have come into use and eliminate many of the disadvantages of the anionic emulsions. Bituminous emulsions formulated using cationic emulsifiers do not "break" in the same manner as anionic emulsions, but rather the bituminous material is deposited from the emulsion due to the attraction of polar charges between the positively charged bituminous droplets and negatively charged aggregate surfaces. Thus, cationic bituminous emulsions deposit more rapidly than the anionic bituminous emulsions on aggregate surfaces and are bonded to the aggregate by the electrostatic action at the interface of the bitumen and the aggregate material.
The aqueous cationic bituminous emulsions themselves are relatively stable, and the emulsion stability may be enhanced by various additives well known in the art. Most cationic bituminous emulsions, however, deposit on the surface of aggregate materials rapidly when aggregate is contacted with the emulsions. Bitumen from an aqueous cationic bituminous emulsion is deposited from the emulsion due to the charge attraction between the bituminous droplets and the aggregate materials. The rapid setting action of cationic bituminous emulsions is of considerable advantage in road building, such as seal coats, since the roads can be opened to traffic shortly after application of the coating. Although the rate of asphalt deposition, for example, from the emulsion can be controlled to some extent, the time required for complete deposition is never very long and it is therefore the practice to combine the cationic emulsion with the aggregate at the site of road construction, either on the surface of the road itself, or in a mobile mixer which permits the emulsion aggregate mix to be rapidly spread. Due to the charge attraction mechanism, the rapidity of deposition of bituminous materials from the cationic emulsion is closely related to the generally negatively charged surface area of the aggregate or filler material. Thus, while a specific cationic bituminous emulsion might provide suitable properties for use in conjunction with some aggregates, the same cationic emulsion may not exhibit suitable properties when used with very finely ground materials having vastly larger total surface area. The rapid deposition characteristics of the cationic bituminous emulsions frequently makes it impossible to use such emulsions with fine-grained aggregate in slurry form such as in gun application or spreader box application. Therefore, since the slurry seal should mix well, pump well, lay down well, not stiffen while being applied, and, after setting, wear well under traffic, it is particularly desirable to be able to control the setting time of the slurry for various aggregates employed.
Acidified reaction products of the above described polycarboxylic acids, anhydrides, sulfonated fatty acids and epoxidized glycerides with certain polyamines are suitable emulsifiers yielding asphalt emulsions which can be mixed with fine grained aggregate to give workable aggregate/emulsion mixes.
These types of emulsifiers are disclosed in U.S. Pat. No. 4,447,269 to Schreuders et al., U.S. Pat. No. 4,450,011 to Schilling et al., U.S. Pat. No. 4,547,224 to Schilling et al., U.S. Pat. No. 4,462,840 to Schilling et al., U.S. Pat. No. 464,286 to Schilling, U.S. Pat. No. 4,561,901 to Schilling, U.S. Pat. No. 4,597,799 to Schilling, and U.S. Pat. No. 4,676,927 to Schilling et al.
However, cationic emulsions produced with these emulsifiers can in many cases only be mixed with the aggregate in the presence of inorganic blending agents such as Portland cement or hydrated lime. These additives are generally employed at a dosage of 0.5-3% based on the weight of the aggregate. The addition of these blending agents has the effect of causing the aggregate/emulsion mix to cure slower, specifically at temperatures below 75.degree. F. Mix and cure behavior is dependent on the type of aggregate and source of the asphalt.
Accordingly, an object of this invention is to provide novel emulsifiers which produce cationic emulsions which can be mixed with aggregate and provide faster curing asphalt/aggregate matrixes at lower temperatures (60.degree.-75.degree. F.) even in the presence of blending agents.
A further object of this invention is to provide a novel mixture of aggregate and bituminous emulsion.
An additional object is to provide a mixture of the above character which is workable under a broad range of conditions.
Another object is to provide a mixture of cationic bituminous emulsion and aggregate with variable setting time.
A particular object is to provide an aqueous bituminous emulsion and fine-grained aggregate slurry mixture which deposits at a fairly rapid rate after being applied to the surface to be treated, and is usable for a longer period of time to enable application in slurry form.